Another reason to only use cellular-based flu vaccine (i.e. flucelvax.)

Science News

from research organizations

How flu shot manufacturing forces influenza to mutate

Egg-based production causes virus to target bird cells, making vaccine less effective

Date:

October 30, 2017

Source:

Scripps Research Institute

Summary:

The common practice of growing influenza vaccine
components in chicken eggs disrupts the major antibody target site on
the virus surface, rendering the flu vaccine less effective in humans.

Share:

FULL STORY

The L194P egg-adaptive mutation
dramatically increases the motility of the major epitope on the
hemagglutinin of influenza H3 viruses. Red: high motility; white: medium
motility; blue: low motility.

Credit: Wilson Lab

According to a new study from
scientists at The Scripps Research Institute (TSRI), the common practice
of growing influenza vaccine components in chicken eggs disrupts the
major antibody target site on the virus surface, rendering the flu
vaccine less effective in humans.

"Now we can explain -- at an atomic level -- why egg-based vaccine
production is causing problems," said TSRI Research Associate Nicholas
Wu, Ph.D., first author of the study, published recently in the journal PLOS Pathogens.

For more than 70 years, manufacturers have made the flu vaccine by
injecting influenza into chicken eggs, allowing the virus to replicate
inside the eggs and then purifying the fluid from the eggs to get enough
of the virus to use in vaccines.

The subtype of influenza in this study, called H3N2, is one of
several subtypes shown to mutate when grown in chicken eggs, and the
researchers say the new findings further support the case for
alternative approaches to growing the virus.

"Any influenza viruses produced in eggs have to adapt to growing in
that environment and hence generate mutations to grow better," explained
study senior author Ian Wilson, D.Phil., Hansen Professor of Structural
Biology at TSRI.

The new study shows exactly why egg-based manufacturing is a problem
for the H3N2 subtype. As H3N2 influenza has become more prevalent,
scientists formulating the seasonal flu vaccine have sought to include
this virus and teach the human immune system to fight it. Despite this
effort, recent flu vaccines have proven only 33 percent effective
against H3N2 viruses.

Wu used a high-resolution imaging technique called X-ray
crystallography to show that -- when grown in eggs -- the H3N2 subtype
mutates a key protein to better attach to receptors in bird cells.
Specifically, there was a mutation called L194P on the virus's
hemagglutinin glycoprotein (HA). This mutation disrupts the region on
the protein that is commonly recognized by our immune system.

This means a vaccine containing the mutated version of the protein
will not be able to trigger an effective immune response. This leaves
the body without protection against circulating strains of H3N2.

In fact, Wu's analysis shows that the current strain of H3N2 used in
vaccines already contains this specific mutation L194P on HA. "Vaccine
producers need to look at this mutation," cautioned Wu.

The researchers say further studies are needed to investigate
replacing the egg-based system. "Other methods are now being used and
explored for production of vaccines in mammalian cells using cell-based
methods and recombinant HA protein vaccines," said Wilson.

Good find! It's about time that they perfected a "universal" flu vaccine, targeting different structural elements of the virus:

Current flu vaccines have to be changed each year to match strains of virus circulating at the time and they do not always protect people that well, especially older patients with weak immune systems.

The new vaccine works by using proteins found in the core of the virus rather than those on its surface. Surface proteins stick out like pins from the virus and change all the time, while those in the core are stable.

I still think responses to a Universal FLU Vaccine will be determined by the genetic make up of the person receiving it.

Different HLA haplotypes will display different epitopes ( parts of the virus) with different efficiencies. What may be a dominant epitope for one person may be a weak epitope for others.

For example live attenuated viruses are used in UK nasal vaccine. This allows the immune system access to all the outer and inner proteins of the virus, but you still don't normally get long term memory responses.

From Hazel (Aah it keeps auto correcting to every name except Hazel. )

You cannot post new topics in this forumYou cannot reply to topics in this forumYou cannot delete your posts in this forumYou cannot edit your posts in this forumYou cannot create polls in this forumYou can vote in polls in this forum